Tenosynovitis with psammomatous calcifications: Series of 18 cases and review of the literature emphasizing a common source of expert consultation and updated differential diagnosis.

Tenosynovitis with psammomatous calcifications (TPC) is a rare, benign condition currently regarded as a pseudotumor possibly related to repetitive use and/or trauma with a predilection for females at acral sites. Thirty-five cases have been reported, with the largest series comprising 23 patients; yet, TPC remains poorly recognized by pathologists and clinicians alike. We report a series of eighteen additional cases along with radiology and clinical follow-up. Our cohort demonstrated a strong female sex predilection (14 females and 4 males), with ages ranging from 12 to 71 years (mean 50 years) and involved the hand/finger (10), toes/foot (5), wrist (2), or elbow (1). More than half (56%) were diagnosed in the expert consultation setting in which contributor suggested diagnoses (8) included: gout/pseudogout (n = 2), chondrosarcoma (N = 1), soft tissue chondroma (N = 1), calcified chondroid mesenchymal neoplasm (N = 1), calcifying aponeurotic fibroma (N = 1), giant cell tumor (N = 1), or "rule out malignancy" (n = 1). The majority of patients presented with painful masses and radiology showed indolent/benign features chiefly within the tendino-ligamentous tissues some with non-specific faint internal matrix/popcorn calcification pattern. None had known metabolic abnormalities and three (of 11) had a history of prior trauma/repetitive activity. The masses were generally small (mean 1.3 cm; range 0.4-2.4 cm) and composed of histiocytoid cells with variable amounts of grungy psammomatous round calcific debris located within tenosynovium. Occasional giant cells and admixed bland (myo)fibroblastic spindle cells were seen. Clinical follow-up (12 patients; mean 30 mos; range 2-61 mos) showed no local recurrences. Herein, we report a large series of well-characterized TPC, review the literature, and offer an updated differential diagnosis of this distinctive, rare, and under-recognized entity cured by simple excision. Increased awareness of TPC should allow confident distinction from morphologic mimics and avoidance of overtreatment.